Adjustable detent control knob

ABSTRACT

AN ADJUSTABLE KNOB FOR APPLICATION TO CONTROL DEVICES SUCH PANEL-MOUNTED RHEOSTATS, POTENTIOMETERS, TUNING CONTROLS, ETC., PROVIDED WITH AN ADJUSTABLE DETENT DEVICE WHICH CAN BE SET IN A SELECTED POSITION OF THE KNOB, AND PERMITS RETURN OF THE KNOB TO THAT POSITION WITHOUT NEED TO OBSERVE OR REMEMBER IT.

Feb. 9, 1971 f J, F. LAWRENCE, JR 3,561,287

I ADJUSTABLE DETENT CONTROL KNOB Filed June 13, 1969 Rf/Magi.

United States Patent 3,561,287 ADJUSTABLE DETENT CONTROL KNOB James F.Lawrence, Jr., 13161 Barrett Hill Circle, Santa Ana, Calif. 92705 FiledJune 13, 1969, Ser. No. 833,003

Int. Cl. Gg 1/10 US. Cl. 74-553 6 Claims ABSTRACT OF THE DISCLOSUREFIELD OF THE INVENTION This invention relates to adjustment knobs forthe rotatable shafts of electrical control devices of potentiometers,rheostats, tuning controls, and the like, and more particularly todevices by which the knob may be returned to a previously selectedposition without observing the position or remembering it.

BACKGROUND OF THE INVENTION It often occurs that a control knob of anelectrical device has one position of rotation at which a specialcondition prevails in an electric circuit controlled thereby, and itbecomes desirable to be able to return the knob quickly to'that positionunerringly, without observation of a dial setting, or the position of apointer, and without listening for an audible signal, or remembering thesetting in any way. It is the purpose of the present invention toprovide an adjustable control knob having such a capability.

BRIEF DESCRIPTION OF THE INVENTION The invention, in a present preferredform, is applicable to a panel-mounted control device having a rotatableshaft. The knob is secured to such shaft in the usual Way. Under thecontrol device mounting nut, adjacent the knob side of the panel, isplaced an arm, preferably a spring arm, and adjacent the rearward faceof the knob is a detent plate cooperable with a detent element on thespring arm. This plate is rotatable 0n the outside of a slightlyprojecting portion of the knobs shaft bushing. The plate has an arcuateslot, concentric with the shaft, and an in ternally screw-threadedsleeve projects through this slot, and has aclamping head or flangewider than the slot. The sleeve projects freely into a bore extendinginto the back face of the knob. This bore meets a reduced counterbore,and a threaded pin, with a knurled head on its end, extends into thecountcrbore, and is screw-threaded into the sleeve. This threaded pin orscrew is screwed into the sleeve until its head engages a shoulder onthe outer face of the knob, and when screwed tight, the detent plate islocked by aie head of the sleeve tightly to the knob. The spring arm hasa depression, hole, or socket, and the plate a protuberance engageablewith this socket. In use, the plate is first unscrewed from fixation tothe knob by loosening the aforesaid screw. The plate is positioned sothat the protuberance thereon engages the depression, hole, or socket inthe spring arm. The knob will then turn relative to the spring arm andthe detent plate. It is rotated to the desired, selected position. Thethreaded pin is then screwed tight, clamping the detent plate to theknob for rotation therewith. When the knob is rotated away from theposition thus selected, it can be returned to that positionindependently of dial markings simply by "ice finding the position, byfeel, at which the detent protuberance on the detent plate finds andenters the socket on the spring arm.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a knob inaccordance with the invention;

FIG. 2 is an exploded view showing component parts of the knob of FIG.1;

FIG. 3 is a view partly in elevation and partly in transverse medialsection, showing the knob in side elevation as mounted on the shaft of apanel-mounted control dev1ce;

FIG. 4 is a view taken in accordance with the section line 44 of FIG. 3;and

FIG. 5 is a detailed section taken on line 55 of FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT The electrical control devicerheostat, or tuning memher is designated generally at 10. This tuningmember has projecting from one face thereof the usual screw-threadedsleeve or bushing 11, in which is journalled the rotatable control shaft12 of the device 10. To mount the device 10 onto the instrument panel13, the latter is provided with an aperture 14 to receive the bushing11, and a washer 15 is positioned between the control device and panel13, around bushing 11. Mounted on bushing 11 on the opposite or frontside of panel 13 is first a washer 16, then a spring arm 17, suitablyperforated at one end to receive the bushing 11, and finally a clampingnut 18 which, when set up, secures the control device and the bushingend of the spring arm tightly to the panel. The spring arm 17 will beseen to be bent outwardly from the panel 13 and into a position suchthat its outer end portion lies in a plane parallel to the panel, andadjacent but spaced slightly in back of the rearward face of the knob,generally designated by the numeral 20. The knob 20 has a usual axialbushing 22 for snug reception of the shaft 12, which is fastened inplace, entirely conventionally, by means of a set screw 24 as seen inFIG. 3.

The knob bushing 22 will be seen to project somewhat beyond the rearwardface of the knob, and rotatable on the projecting extremity of thebushing is a detent disc 26, of a diameter preferably equal to orslightly less than the diameter of the conventional dial flange 28 atthe rear of knob 20. The disc 26 has an arcuate slot 29 thereinextending, in this case, for approximately 270 of angle, the arcuateedges of the slot being struck about the central axis of the knob as acenter. As here shown, the knob has on its rearward face a slightlyraised hublike portion 30, and the aforementioned detent disc 26 liesimmediately adjacent the face of this hub-like portion 30, and thusnormally stands spaced slightly in back of the dial flange 28 of theknob. Radially outside this portion 30, the disc 26 is capable of aslight yielding or resilient deflection towards and finally against therearward face 32 of the dial flange 28 of the knob (FIG. 5). Disc 26 hasa small protuberance 34 which is engageable in a hole or socket 35 inthe end portion of the spring arm 17 when rotated to the postion of FIG.3. As will appear, the spring arm 17 functions as an index or referencemember. Rotation of the disc 26 from this position, relative to thepanel and to the fixed spring arm 17 will result in separation of theprotuberance 34 from the socket 35 with a slight resistance permittedeither by resilient deflection of the disc 26, or of the spring arm 17,or both. Similarly, assuming the disc 26 to be initially in a positionin which the protuberance 34 is out of registration with the socket 35,the disc can be rotated into the position of registration, slightdeflection of the spring arm, the disc, or both permitting theprotuberance to ride over the spring arm to the socket. Preferably, thedisc 26 has at its periphery a tab 38 bent over the dial flange 28, in aconvenient position to be reached by the fingers of the operator tofacilitate the rotation of the disc 26 when desired.

A means is provided for clamping the disc 26 against rotation relativeto knob 20, and as here shown comprises a screw means in the form of aninternally threaded sleeve 40 mounted for axial movement in a boreextending into the rearward side of the knob, in a position offcenterfrom the axis of the knob, and so as to extend through theaforementioned arcuate slot 29. On the outer end of this sleeve 40 is aclamping head or flange 41, which is wider than the slot 29 so as tooverlap the margins thereof, and which is engageable with the disc 26.The sleeve 40 thus projects freely or with a light frictional fit, intoa bore 42 extending into the back face of the knob. This bore 42 meets areduced counterbore 43 extending into the knob from its front face.Preferably, and as here shown, the counterbore 43 meets an enlargedcounterbore 45 immediately adjacent the front face of the knob. A thumbscrew 46 is screwed into the sleeve or bushing 40 through counterbores43 and 45. The screw has a knurled head 48 and as a part of the head, orjust inside it, an integral flange 49 which seats against the bottom ofthe counterbore 45. Rotation of the screw head 48 draws the sleeve 40inwardly into the knob so that its head 41 acts to clamp the disc 26tightly to the rearward face of the knob dial 28. Rotation in thereverse direction of course unclamps the disc 26 for free rotation.

In the contemplated mode of use of the knob, the disc 26 is firstpositioned with its protuberance 34 seated in the socket 35. The screw46 being loosened, the knob can then be turned relative to the springarm and the detent plate or disc 26 bearing the protuberance. Clearly,the engagement of the protuberance in the socket in the spring armprevents rotation of the disc with the knob at this time, frictionalengagement between the disc and the knob being insufficient to causedisengagement of the protuberance 34 from the socket 35. The knob isthus rotated to a desired, selected position, the detent disc 26remaining in its fixed position relative to the spring arm. The screw 46is then screwed tight, clamping the detent plate to the knob forrotation therewith (FIG. When the knob is thereafter rotated away fromthe position thus selected, it can be returned to that positionindependently of dial markings simply by finding the position, by feel,at which the detent protuberance on the detent plate finds and entersthe socket on the spring arm 17.

The spring arm 17 is so formed as to assure seating of the protuberance34 in the socket 35 when the disc 26 is thus clamped to the back of theknob. This of course means that the spring arm 17 is so formed andmounted as to stand normally in a position close to the rearward side ofthe knob, i.e. such that when the disc 26 is clamped against the knob,the spring arm 17 will be in a position such that the protuberance 34will re-engage with the socket 35 when these elements are registered.

It will be seen that I have thus provided a control knob which can beoperated to position an electrical device in a selected position, andthereafter quickly set in such a way that the knob, after being rotatedaway from the selected position, can be returned quickly and preciselyto the selected position without benefit of dial markings, and withoutbenefit of recall of the location of the selected position ofadjustment.

I claim:

1. A position finder for an electrical control device mounted on a fixedsupport and having a rotatably adjustable control shaft extendingtherefrom, comprising:

a knob adapted to be fixed onto said shaft;

4 a detent plate positioned immediately rearward of said knob andarranged for rotation relative to the knob about the axis of saidcontrol shaft;

releasable clamping means on said knob for clamping said plate to saidknob to rotate therewith;

index means mounted tightly relative to said fixed support and having aportion positioned adjacent to said detent plate; and

cooperable detent elements on said index means and detent plate spacedradially from said shaft, said elements being interengageable at apredetermined position of rotation of said detent plate to automaticallyyieldingly lock to one another and thereby exercise a yielding restraintagainst rotative displacement of said plate from said position.

2. The subject matter of claim 1, wherein the portion of said indexmeans having one of said detent elements is resiliently deflectable indirections toward and from said knob to facilitate engagement anddisengagement of said detent elements.

3. The subject matter of claim 1, wherein the portion of said detentplate having one of said detent elements is resiliently deflectable indirections toward and from said knob to facilitate engagement anddisengagement of said detent elements.

4. The subject matter of claim 1, wherein the portions of said indexmeans and detent plate having said detent elements are resilientlydeflectable in directions toward and from said knob to facilitateengagement and disengagement of said detent elements.

5. The subject matter of claim 1, wherein the control device is to bemounted on an apertured panel, and wherein said control device has athreaded sleeve surrounding a portion of said shaft where the shaftprotrudes from the control device, said sleeve protruding through theaperture in the panel;

said index means comprising a spring arm mounted at one end on saidsleeve;

a nut on said sleeve for clamping said spring arm to said panel; and

said spring arm extending radially from said sleeve, and its outer endportion lying adjacent to said detent plate.

6. The subject matter of claim 5, wherein:

said releasable clamping means comprises a thumb screw mounted in saidknob, on an axis parallel to but spaced radially outward from thecentral portion of the knob, for rotation relative to the knob butsupported against axial translation therein from front to rear;

a threaded screw means in said knob threadedly engaged with said thumbscrew, said screw means having a clamping head; and

said detent plate having an arcuate slot therein, concentric with saidshaft, which receives an outer portion of said screw means, with saidhead on said screw means overlapping a margin of said slot, so as toengage said detent plate.

References Cited UNITED STATES PATENTS 1,365,543 1/1921 Regenold28753(H) 2,620,672 12/4952 McMahon 7410.41

FRED C. MATTERN, JR., Primary Examiner F. D. SHOEMAKER, AssistantExaminer

